This invention relates to a novel photo-insolubilizable composition comprising a photoinsolubilizable resin containing as a photo-crosslinking residue a styryl type nitrogen-containing heterocyclic residue in the molecular unit thereof and an acid, to a novel photosensitive high molecular compound exhibiting outstanding sensitivity for an extremely small photosensitive group content, and to a method therefor.
Photosensitive resins (photo-insolubilizable high molecular compounds) have found acceptance for actual use as materials for printing plates, as photoresists such as for photoetching and phototrimming, and as photosensitive vehicles such as for paints and printing inks. Among the photosensitive resins which have found utility in actual applications, those using azide group, cinnamoyl group, acryloyl group, etc. as photo-crosslinking residues are typical. For these resins to be sufficiently practical, such photo-crosslinking residues are required to be contained in fairly large amounts in the backbone polymers of the resins. Further, these photosensitive resins are actually put to use as combined with sensitizers. In order that polyvinyl cinnamate incorporating a cinnamoyl group and constituting itself a typical photosensitive resin may be actually used advantageously as a photosensitive resin, it is imperative that the backbone polymer of the resin should incorporate the cinnamoyl group as a photo-crosslinking residue in a large amount (M. Tsuda: J. Poly Sci. A., 2, 2904 '64). Moreover, the resin should be put to use in combination with about 10% by weight of a sensitizer.
This fact implies that such a known photosensitive resin necessitates use of a large amount of a raw material for the incorporation of a photo-crosslinking residue far more expensive than the raw materials for the resin itself and that the incorporatiion of such a large amount of photo-crosslinking residue in most cases degrades the properties inherent in the backbone polymer such as, for example, intimate adhesiveness to substrates, developing property, chemical resistance, and printability.
To overcome the disadvantages described above, photosensitive resins incorporating special photo-crosslinking residues such as, for example polyvinyl alcohol incorporating a styryl type quaternary salt residue have been suggested (Japanese Patent Publication No. SHO 56(1981)-5761 and Japanese Patent Public Disclosure SHO 56(1981)-11906).
Photosensitive resins using polyvinyl alcohols as their backbone polymers, however, have such high degrees of hydrophilicity that they suffer from the disadvantage that water or water-containing aqueous organic solvents are seldom usable as their developing liquids.
The inventor conducted a study in search for a photosensitive resin which is solubilizable in any given organic solvent and is highly sensitive for a very small photosensitive group content in its backbone polymer, and a photosensitive composition using the photosensitive resin. After the study, they have perfected this invention.